Last night ended up clearing rather suddenly about a quarter past 9pm. I hadn't planned on it being clear, and I wasn't sure if it was going to stay clear...but when the skies remained spotless by 9:30pm, I put out my gear. I had been imaging Sh2-132 and Pacman nebulas, however I promised many of you ASI1600 fans a while back that I would so some high gain NB imaging with short exposures to see how it went. When I set up, Sh2-132 was a bit far along, and Pacman wasn't quite clear of the trees yet...so I zeroed in on Bubble Nebula, about midway between the two. I usually use a high gain setting of 300 to do my framing and focusing, as with relatively short exposures you can still see the objects you are imaging, and with 1s subs you can focus the stars in real time. Rather handy.
Well, I noticed how clean Bubble looked with only 90 second test subs when I was framing...and decided to embark on a little high gain, short exposure narrow band project. I stuck with the high gain, although backed it off to setting 200, and stuck with the 90 second subs. I decided to acquire 16 Ha (3nm AstroDon, 150mm f/4 refractor) from my red zone, which last night looked like it was around 18.9mag/sq". While the first 16 subs were exposing (my original plan was to switch to Pacman OIII once it cleared the trees), I fiddled around with the first sub:
Not bad at all for 90 seconds, grand total integration, for a 3nm narrow band filter! I decided to forego Pacman, and get some SII and OIII on Bubble at the same gain setting and with the same exposure lengths. The project turned out to be quite a success. I acquired 36 subs in all three channels, 54 minutes each. The full Ha stack, 46.5 minutes worth (31 good subs) turned out very nice:
I decided to try and balance the SNRs of each channel, so I stacked 9x90s Ha, 25x90s OIII, and 36x90s SII...progressing from highest SNR per sub to lowest. The SII here was quite faint...a good deal fainter than the OIII, but definitely still there. I decided to first generate a master luminance from all three channels after an initial blend:
The SII really brings in a lot more stars than either Ha or OIII. Both contain the same stars, but not nearly as intense as in SII. I've noticed that before when working other NB images...but the difference was quite stark this time. For 1h45m grand total of integration, I think the experiment was a success! I am currently processing an SHO custom blend version, and will share the results once I have a final version. Until then...if you are stuck in the city and have limited time...consider high gain imaging with a modern CMOS camera from ZWO or QHY. I acquired a full set of data across all three primary NB channels for Bubble and the field surrounding it in a matter of 4 hours active imaging time (and only 1h45m worth of integrated data)! Never did I imagine that I'd be able to create a full color tri-channel NB image with so little time invested...however things are changing. New technology is really opening up some doors.